superuser

n. account that has access to restricted activities; person who has an account with access to restricted activities (Computers)

On many computer operating systems, superuser, or root, is the term used for the special user account that is controlled by the system administrator.Many older operating systems on computers intended for personal and home use, including MS-DOS and Windows 9x, are not multi-user operating systems, and there is no distinguished superuser account. Effectively any user of the system has administrator privileges. Separation of administrative privileges from normal user privileges makes an operating system more resistant to viruses and other malicious software, and the lack of this separation in these operating systems has been cited as one major reason why these operating systems are less secure.
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[Unix] Synonym root, avatar. This usage has spread to non-Unix environments; the superuser is any account with all wheel bits on. A more specific term than wheel.
[Jargon File]